You mustn't mix up life steal and spell vamp.
Life steal steals on physical damage (meaning auto-attack for vlad). In fights, you very rarely use your auto-attacks to deal big damage because you're a caster.
Spell vamp steals on magical damage (meaning all of his spells), this is want you want if your plan is to steal more life.
- Zhonya's Hourglass is great because vlad's ult has low range but must be cast in battle engage to hit the most enemies and for the 15% extra magical damage. The two second invulnerability will allow you to stay alive in the heart of the battle if you get targeted.
- I also very often use Hextech Revolver with Vlad, but you need some AP. It's no use having 50% Spell vamp if you don't deal any damage.
Vlad spells cost life, the good thing about more spell vamp is you can get your life back faster with transfusions minion lines and you can cast life costing spells (specially Tides of Blood that stacks) with less impact on your life.
EDIT : I went to have a quick look at all the different Vlad builds. All (or nearly all) of the descent builds have hextech revolver in them with its evolution to will of the ancients - give more AP, more spell vamp and an aura :-)
Each support champion plays a different role (e.g Teemo would play differently than Sona, Soraka would play differently than Fiddlesticks). If you're looking at a specific support, perhaps you should ask "How do you play Sona as support effectively?".
In general, if you're claiming the role of support your biggest responsibility is do cater to the whims of the range AD you will roll with bottom lane. Often times when I play support I'll ask the range AD which he/she would prefer (Some like having the auras and diversity Sona can provide, while some like the extra control Janna can offer, and others like the extra mana from Soraka).
Regardless of the support champion you end up with there are a few important jobs you have:
- Ward: Vision is key to preventing ganks and following enemey movements, as you're support and $$ is less important to you than other roles, spend it on wards (here is a guide on it Where/How to ward
- Clairvoyence(CV): Get the ability it'll help with finding junglers, keeping up with dragon/blue/red/baron spawns, and also is useful to toss in Top's river every once in awhile(saves him from being ganked)
- Let your partner get last hits, in fact unless necessary don't even bother hitting minions unless you're pushing. If you're doing damage and your partner is trying to last hit, your damage may mess up their timing.
- Be map aware: This ties in with Ward and cv, but keep an eye on where champions are in case you need to alert your partner to back off. Also, you may get pings to cv certain locations, so pay attention.
- When possible buy an oracles elixer to help kill enemy wards. This will prevent them from being map aware!
- Do what your class is made to do. As this is class specific, I'm not going to elaborate but if your skills can benefit your lane partner use them when needed.
Playing support will take some getting used to, but they can be fun. Don't expect to be the highest level on your team, don't expect to have a full set of items quickly, don't expect to be rich. Unless your character can handle it, you shouldn't be near the front of team fights.
This is only some basic tips, and I'm sure I'm missing some, but it will get you going.
Best Answer
If it is just Q upgrade to max, I would start with Deathcap, deathfire grasp, zhonya's hourglass, magic pen boots, magic pen Percentage staff, and liandra's torment.
Since people at the top comment requested the reasoning was simple all 4 items deal its most maximum on ap therefore you get a bigger bonus with deathcap, magic pen percent shreds over their existing magic resist plus more if they don't have any and amplify your damage, and Liandra's torment is for the magic penetration as well as hp shread for 5% if you are dealing with tanks with hp and magic resist.
Also spamming spells over time would mean that you would need a blue buff to continuously spam spells but I highly doubt you will be mana depleted with this gear type and whoever your opponent is fighting wouldn't die.